Example GTM and LTM configuration

There are a number of variables related to what you're asking for. I recommend going through the free online GTM training provided by F5:

https://f5.com/education/training/free-courses/tag/global%20traffic%20manager

and reading this guide:

https://support.f5.com/kb/en-us/products/big-ip_gtm/manuals/product/gtm-implementations-11-5-0.html

You may consider the three day GTM training course provided by F5:

https://f5.com/education/training/courses/big-ip-global-traffic-manager-gtm-v11

Having said that, here are some simple configuration commands via tmsh for configuring a GTM for initial use, then adding an LTM to its iQuery mesh, with the following assumptions:

GTM:
  - mgmt IP:        192.168.1.212
  - VLANs:          internal, external
  - selfIPs:        internal = 10.10.212.1/24; external = 10.11.212.1/24
  - route:          default via 10.11.212.254
  - provisioned:    GTM
LTM:
  - mgmt IP         192.168.10.100
  - VLANs:          internal, external
  - selfIPs:        internal = 172.16.5.1/24; external = 172.20.50.1/24
  - route:          default via 172.20.50.254
  - provisioned:    LTM

And the commands:

  Create a Datacenter; all Servers must be in a Datacenter
 tmsh create datacenter seattle
 
  Create Server for the GTM itself; it will not monitor objects unless this is done
 tmsh create gtm server gtm01 addresses add \
    { 192.168.1.212 { } 10.10.212.1 { } 10.11.212.1 { } } \
    datacenter seattle product single-bigip monitor bigip
    
  Create Server for the LTM; this is a required before running bigip_add
 tmsh create gtm server ltm01 addresses add { 172.20.50.1 { } }
 
  Run bigip_add
 bigip_add 172.20.50.1

If you are using certificates that are not self-signed:

https://support.f5.com/kb/en-us/solutions/public/7000/700/sol7717.html

If the LTM is running an older version of BIG-IP than the GTM, you may need to run

big3d_install

https://support.f5.com/kb/en-us/solutions/public/13000/300/sol13312.html

The LTM interface through which iQuery communication occurs must have port lockdown set at least to "Default" (i.e., it cannot be "None").

From this point, you must create GTM Pools containing the LTM Virtual Server objects, then create WideIPs using the created Pools. The materials above should prove instructive for this purpose.